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Thread: Cylindrical Pressure Vessel with Stiffeners stress calculations

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    Cylindrical Pressure Vessel with Stiffeners stress calculations

    I'm running some calculations for a cylindrical pressure vessel of any radius and internal pressure. I'm trying to perform some stress analysis on the body with ring stiffeners welded to the exterior surface. I am having trouble finding related literature to the subject apart from some details regarding hoop stress on a bare cylindrical vessel. I can run calculations on the bare pressure vessel just fine but the addition of stiffeners and examining the stresses on them and the siding of the pressure vessel in between each stiffener is proving challenging. Any help or suggestions on how to perform these calculations would be greatly appreciated.

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    Um, hate to say it, and I mean NO disrespect, but if you are asking these basic questions, (applies to your other post as well) it may not be such a good idea to be designing pressure vessels.

    Pressure vessels have the potential for some very serious damage. Damage that usually occurs without any prior warning, holding pressure, holding pressure, then suddenly, "whoomp" not holdng pressure and sharp heavy stuff flying everywhere at very high speeds.

    You will probably need to have the vessel certified before use, so you would be well advised to hire an Engineering firm that specializes in such vessels.

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    Administrator Kelly Bramble's Avatar
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    ASME Boiler and Pressure Vessel Code (BPVC)

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    Technical Fellow jboggs's Avatar
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    You should take Dave's advice to heart. Of all the massive and deadly engineering failures in the past, pressure vessels hold their own special place of "merit".

    Picture yourself on the witness stand telling the lawyer for victims' families that you got your formulas off the internet.

    Why do you think the Boston bombers used pressure cookers?

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    The calculations I'm running are for dust collectors, which are generally rectangular in shape and have stiffeners added to the sides for strengthening. I apologize for not stating that in the original post.

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    None of my calculations are being used in actual design. I am a student engineer who has been asked to research into how these devices are designed. I am not a professional and I'm merely performing calculations for a firm that I'm currently doing a work term with. Everything is being reviewed by professional engineers before being presented in any report or otherwise. All of my questions are merely to understand the theory behind the designs of pressure vessels; dust collectors specifically. Any help with this is appreciated.

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    Technical Fellow jboggs's Avatar
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    What internal pressure are you dealing with? You never specified that. Being a student, you might not be aware of the fact that most "pressure vessels" are designed to meet the requirements of certain codes, which can vary by locality. Those codes also clarify what is considered a pressure vessel, and which class or category, by the design pressure rating and application. Maybe others on this forum have heard of it , but I never heard a dust collector being called a "pressure vessel". There might be a slight delta-P inside it compared to atmospheric but I doubt if it ever approaches the threshold to become a real pressure vessel. For another thing, the internal pressure is never sealed inside. Right? Maybe some of the guys you're working with described it that way to give you an idea what you are working with.

    For what you're working with I think you need to design it to be robust enough to withstand whatever environmental and handling factors may apply. That will probably be more than stiff enough to withstand what I see as a miniscule internal pressure.

    Other readers with more experience may have other opinions, but that's how I see it.

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    +1 JB, and a good-day to you all to force this over the minimum 10-characters required for a valid comment.

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    Administrator Kelly Bramble's Avatar
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    Quote Originally Posted by PinkertonD View Post
    +1 JB, and a good-day to you all to force this over the minimum 10-characters required for a valid comment.
    What? Trying to minimize the grunts, nods and other stuff...

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    Administrator Kelly Bramble's Avatar
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    I've figured out what I was originally having trouble with. I had to focus on stress concentrations caused by both operating pressure and the maximum pressure that would be experienced if an explosion should occur. The stiffeners had to be examined for yielding (typically I had to operate at around 80% of the yield point of carbon steel, which is 294.8 MPa). The operating pressure was 1.08 psi and the max was 3.92 psi. My calculations were able to predict that the stresses experienced were lower than 80% of yield at any point on the dust collector.

    I understand that it's not "sealed" (inlet/outlet of dirty air) but a certain pressure does accumulate inside. My coworkers described it as a "pressure vessel". I apologize for the earlier confusion but thank you for your suggestions.

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    At the risk of reducing this topic below "family" level, but wouldn't an explosion at 3.92-psi be more of a fart than a bang?

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    Administrator Kelly Bramble's Avatar
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    I would think passing gas is in the 1-2 psi range in the south.... What part of the world do you live Dave?

    Quote Originally Posted by PinkertonD View Post
    At the risk of reducing this topic below "family" level, but wouldn't an explosion at 3.92-psi be more of a fart than a bang?

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    It seems that two people who really should know better, have wrecked this thread!

    Good thing the OP posted in two different threads with a similar Subject, at least some sanity (sanitary??) is prevailing over on the other one.

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